1. Field of the Invention
The present invention generally relates to multiple-phase electrical distribution devices and, more particularly, is concerned with an air insulated padmounted switchgear having an adjustable insulating barrier arrangement employed therein.
2. Description of the Prior Art
Multi-phase padmounted switchgear is conventionally used in underground electrical distribution systems to permit ground level access to switching components in order to permit visual inspection and maintenance thereof. The electrical distribution system can be operated conveniently by a lineman standing on the ground adjacent to an enclosure of the padmounted switchgear. U.S. Pat. No. 4,886,945 to Roberts et al, U.S. Pat. No. 5,181,158 to Goe, Jr. et al and U.S. Pat. No. 5,181,164 to Beard et al, all of which are assigned to the assignee of the subject application, disclose such padmounted switchgear.
The multi-phase padmounted switchgear includes an enclosure with a plurality of side-by-side spaced three-phase switchgear assemblies disposed therein. Each switchgear assembly typically includes an upper conductor supported in the enclosure by an insulator secured to the top of the enclosure and a lower contact electrically connectable to the upper conductor. The upper conductor includes a fixed contact having an arc chute and the lower contact includes a switch blade that is pivotable about a shaft between a closed position in which it is disposed adjacent to the arc chute and an opened position in which it is pivoted downwardly away from the arc chute. When in the closed position, the switch blade is in engagement with the fixed contact such that electrical current flows through the switchgear assembly. When in the opened position, the switch blade is pivoted out of engagement with fixed contact such that electrical current flow is interrupted through the switchgear assembly.
One safety aspect associated with the use of such padmounted switchgear involves the need for separating the phases of electricity within the apparatus from one another in order to prevent physical contact or electrical communication between the phases. Electrically conductive gases are typically formed inside the arc chutes during electrical current interruption. If unimpeded, these gases can quickly migrate inside the switch enclosure and cause undesirable and possibly dangerous electrical flashover between the switch phases. Thus, upper and lower barrier panels made of insulated material are vertically mounted between the switch phases with the lower edges of the upper barrier panels overlapping the upper edges of the lower barrier panels to prevent migration of the conductive gases past them and from one switch phase to the next.
The upper and lower barrier panels are designed to be in place at all times except while maintenance is being performed on the lower portions of the switchgear assemblies or the attached cables. During these periods of maintenance, another or an additional insulated barrier panel, portable in construction, is needed, this time for placement in a generally transverse or horizontal position, between the vertically-mounted upper and lower barrier panels, to electrically isolate the lower portion of the switchgear assemblies from the upper portion thereof and to prevent the switch blades from inadvertently closing and thus energizing the areas being serviced.
The lineman performing the maintenance must insert the additional portable barrier panel when needed. A problem arises due to the fact that the upper and lower barrier panels are factory-installed to intersect or overlap with one another to block gas migration. In order for the lineman to properly install the portable barrier panel, the factory-installed upper and lower vertical barrier panels need to be moved and relocated slightly to create a gap between them to receive the portable barrier panel.
Consequently, a need exists for a solution to the problem of how to create such gap between the factory-installed upper and lower vertical barrier panels and still block gas migration.